1. Field of the Invention
This invention relates to a focus adjusting control device for adjusting the focal point of optical means for an object which is captured in a sighting part of a picture plane specified by the optical means and more particularly to an improvement in a focus adjusting control device of the kind arranged to permit selection of the position of the sighting part on the picture plane.
2. Description of the Related Art
The conventional camera having an automatic focus detecting (AF) device is provided with the above-stated sighting part (hereinafter referred to as a distance measuring mark or a focus detection area) which is set near to the center of a photo-taking picture plane. In most cases, a photographing operation is performed by placing an object to be photographed at the distance measuring mark. However, the object is occasionally located in some part of the picture plane other than the central part thereof. In that case, a photographing shot would result in a blurred picture as the AF device takes aim at the above-state distance measuring mark regardless of the actual location of the object.
To solve this problem, some known cameras are arranged to permit focusing at parts other than the center of the picture plane. The camera of this kind is provided with a so-called focus lock device for enabling the photographer to first place the object at the distance measuring mark (or a focus detection area) to have the lens of the camera focus on the object and, after that, to change the composition of a picture before taking the picture with the focus position kept unchanged. However, since the layout of objects is to be adjusted after focus locking, a shutter opportunity tends to be missed.
Further, some known cameras are arranged to automatically measure distances to a plurality of objects, to obtain information on the nearest object distance from the plurality of object distances and to focus the lens on the nearest object. However, the object to be brought into focus is not always located at the nearest distance. The camera of that kind, therefore, has caused inconvenience in some cases.
Further, a camera which is arranged to have the position of the above-stated distance measuring mark shiftable within the picture plane to adjust it to the position of the object to be photographed has been disclosed in Japanese Laid-Open Patent Application No. SHO 60-18423. This camera, however, requires the focusing operation to be repeated every time the distance measuring mark is shifted from one position to another and is thus considered unsatisfactory in terms of operability.